Pulley

ABSTRACT

A pulley consists of a pulley basic body which has a cylindrical outer circumferential surface. Sitting on this cylindrical outer circumferential surface is a tire which is of sandwich-like design with regard to its radial extent. This results in a plurality of rings concentric to one another. The ring which is furthest on the inside in the radial direction and the ring which is furthest on the outside in the radial direction are in each case elastomeric rings, whereas a reinforcing ring is located between them. The elastomeric outer ring is harder than the elastomeric inner ring, so that a very abrasion-resistant surface is achieved, over which the rope runs, whereas the elastomeric inner ring provides for adequate resilience. The reinforcing ring is provided in order to distribute the rope load as uniformly as possible over the elastomeric inner ring.

BACKGROUND OF THE INVENTION

Pulleys are required for guiding and supporting ropes in aerial tramwaysfor the transport of materials and passengers. As shown by EP-A-O 185531, such pulleys consist of a basic body which has a wheel hub withwhich the pulley is mounted so as to be rotatable on a fixed spindle.Emanating from the wheel hub are spokes, which are designed ascompression spokes and connect the wheel hub to an outer ring of thebasic body. This outer ring forms a cylindrical outer circumferentialsurface, which is defined in the axial direction and thus laterally bytwo flange disks. The flange disks are a one-piece component of theouter ring.

A tire made of a hard elastomeric material sits in the slot defined inthis way, the outer circumferential surface of which tire forms a ropegroove. The inner circumferential surface of this tire is a cylindricalsurface and has a slightly larger diameter than the slot contained inthe outer circumference of the outer pulley ring. A further ring, whichis to be elastic, sits in this gap.

The radially outer ring of the rope groove is to be sufficientlywear-resistant, whereas the other, radially inner ring is to produce acertain radial resilience.

However, it has been found here that, in such pulleys, the radialresilience is not sufficient to absorb forces which are produced owingto the fact that a clamping socket acting on the rope runs over thepulley.

The clamping sockets, via which the gondolas hanging on the rope areconnected to the rope, constitute local thickening from the point ofview of the pulley. When they run over the pulley, on account of thethickening, either the load hanging on the rope must be raisedaccordingly or the pulley must move downward. This results inconsiderable forces, since the change in the distance between the centerof the pulley and the core of the rope must take place relativelyquickly. Even if the pulley as a whole is mounted in an elastic manner,the forces are enormous.

A further problem with such pulleys is the flexing work which theelastomeric material is subjected to during the running. At thatlocation at which the rope rests, the elastomeric tire is compressedand, on account of the rotation of the pulley, this compressed region ofthe elastomeric tire runs around along the tire, as a result of whichflexing work is produced. The flexing work inevitably leads to heatingand corresponding wear of the elastomeric tire.

SUMMARY OF THE INVENTION

An object of the invention is to provide a pulley which behaves in amore favorable manner with regard to the running quality and the wear.

This object is achieved according to the invention by the pulley whereinthe tire sitting on the outer circumferential surface consists of tworings, a radially outer and a radially inner ring. The radially outerring contains the rope groove and is comparatively hard andwear-resistant.

Suitable materials for the outer ring are plastics and correspondinglyhard elastomers.

On the other hand, the radially inner ring is made of a comparativelysoft elastomer, which is to have as little damping as possible. When theclamping socket runs over it, the radially inner ring is intended tomerely yield in an elastic manner, but is to perform as little dampingwork as possible.

So that the flexing work, which is achieved by the compression of theradially inner ring, is distributed as far as possible over the entireradially inner ring and is not only effective in a very pronounced localmanner, a reinforcing ring is provided, which is located in the tire.This reinforcing ring may be embedded both between the radially outerring and the radially inner ring and inside one of the rings.

The reinforcing ring achieves the effect that the outer elastomeric ringlargely retains its circular form and is subjected to scarcely anyflexing work.

Since a material having little internal damping may be selected for theinner ring, less flexing work is produced and thus less heating isproduced during operation of the pulley.

In order to produce the greater softness of the inner elastomeric ring,the inner elastomeric ring may either be made of a softer material or itmay be made softer by corresponding bores or chambers which arecontained in it.

A further improvement in the running properties is achieved if the tirecontains a reinforcing ring. This reinforcing ring ensures that theforce originating from the supported rope is distributed uniformly overthe inner ring. As a result of the reinforcing ring, the inner ring isnot deformed locally in that region which is located directly below therope supporting point, but rather the deformation extends over theentire circumferential length of the inner ring.

The reinforcing ring may be a plastic molding, a sheet-metal formed partor a metal casting or forging, the plastic molding being somewhat moreresilient than the metal part. The selection of the hardness of theplastic molding can determine which circumferential region of the innerelastomeric ring is deformed as a result of the rope supporting force.

The form of the reinforcing ring is advantageously selected in such away that the radially inner elastomeric ring and/or the radially outerring has an approximately constant thickness as viewed over its axiallength.

In order to make it possible to easily remove the tire from the pulleybody without impairing the firm seating of the tire on the pulley body,a clamping device is expediently provided. This clamping device actsessentially in the radial direction.

In the simplest case, the clamping device has an annular, essentiallyrotationally symmetrical form having a radially inner surface and aradially outer surface. It is either fitted in between the tire and thepulley body or is located virtually inside the tire.

In order to achieve the clamping effect, the clamping device is split intwo, the radial pretension force being produced by these parts beingclamped together axially, and this pretension force acts radially inwardagainst the pulley body on the one hand and outward toward the tire onthe other hand.

The simplest way to achieve the clamping effect is to split the clampingdevice into two rings, the thickness of which varies in the axialdirection. In the simplest case, each of the rings has an outerfrustoconical form and a frustoconical bore, the cones defining thesesurfaces being in opposition. When the two rings of the clamping deviceare assembled so as to be facing one another with their thinner end, aconstriction is obtained approximately in the center relative to theiraxial extent. If the tire or the pulley body is designed in acorrespondingly complementary manner, a movement of the two rings of theclamping device toward one another produces the desired radial clampingforces relative to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the subject matter of the invention are shownin the drawing, in which:

FIG. 1 shows a pulley according to the invention in a perspectivetruncated representation,

FIG. 2 shows the tire of the pulley according to FIG. 1 in an enlarged,truncated, perspective representation,

FIGS. 3 and 4 show other exemplary embodiments for the tire of thepulley according to the invention in a cross section, and

FIG. 5 shows a pulley according to the invention with radially actingclamping device, in an exploded representation and in longitudinalsection.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A pulley 1 for aerial tramways is illustrated in FIG. 1 in a perspectivetruncated representation.

The pulley 1 has a pulley body 2 and a tire 3 fastened to the latter.The pulley body 2 is a one-piece casting, which forms a central,approximately cylindrical hub 4 with a continuous bearing bore 5. Aplurality of spokes 6, which are designed as compression spokes, emanateradially outward from the hub 4 to an outer pulley ring 7, which isconnected in one piece with the hub 4 via the compression spokes 6. Thepulley ring 7 forms a cylindrical seating face 8 for the tire 3. Thecylindrical seating face 8 is concentric to the bearing bore 5.

The pulley ring 7 is defined in the axial direction by two flank faces9, which are essentially parallel to one another and, starting from thecylindrical seating face 8, extend by a short distance in the radialdirection toward the hub 4.

In the exemplary embodiment shown, the flank faces 9 are annular flatfaces which are parallel to one another and are at a distance apartcorresponding to the axial length of the seating face 8. However, theymay also be frustoconical surfaces which are oriented in such a way thatthe imaginary apex of the cone lies on the respectively other side ofthe pulley 1.

In each case a flange disk 12 is fastened to each flank face 9 by meansof several screws 11 distributed equidistantly. The two flange disks 12serve to axially secure the tire 3 and are also intended to additionallysecure the rope running over it in order to prevent the latter fromfalling off at the side.

In a typical pulley, the effective diameter ranges between 100 and 700mm.

In FIG. 2, the tire 3 is shown in a perspective, cut-open, enlargedrepresentation. The axis of rotation of the pulley 1 lies in the sectionplane.

Relative to the radial direction, the tire 3 is of sandwich-likeconstruction and is essentially formed by three rings 13, 14 and 15lying concentrically one inside the other. The radially inner ring 13 ismade of an elastomeric material having a Shore hardness of between 40and 75. It is defined by a radially inner cylindrical surface 16, acylindrical surface 17 pointing radially outward, and two flank faces 18and 19 lying in the axial direction. In addition, two lateral strips 21and 22 are integrally formed on the outside of the inner elastomericring 13, and these lateral strips 21 and 22 lengthen the two flank faces18, 19 radially outward by a short distance. The strips 21 and 22 mergeinto lips 23 and 24 pointing axially outward. In addition, the ring 13contains a textile reinforcement (not shown) next to the innercircumferential surface 16.

In the region between the cylindrical surface 16 and the lips 23, 24,the cross section of the inner elastomeric ring 13 is approximatelytrapezoidal in such a way that the inner elastomeric ring 13 has itsgreatest axial extent in the region of the cylindrical surface 16. It isslightly narrower at the level of the axially outer cylindrical surface17.

To improve the heat dissipation and to improve the resilience, theelastomeric ring 13 is provided with a multiplicity of through-openings25, which are parallel to the axis, are distributed equidistantly alongthe circumference of the elastomeric ring 13 and lead from the flankface or end face 18 to the flank face or end face 19.

The diameter of the cylindrical surface 16 is just as large as theoutside diameter of the seating face 8 or slightly smaller, justsufficient for an interference fit of the tire 3 on the pulley body 3 tobe achieved.

The ring 14, which is slightly further on the outside in the radialdirection and adjoins the ring 13, is a reinforcing ring. It consists ofa plastic molding, which has the contoured cross-sectional form whichcan be seen from FIG. 2. The cross-sectional form of the reinforcingring 14 is constant along the entire circumference.

The reinforcing ring 14 is defined on its radially inner side by acylindrical surface 26, two side or flank faces 27 and 28, and aradially outer circumferential surface 29. The radially innercircumferential surface 26 is the complementary cylindrical surface tothe circumferential surface 17 of the inner ring 13. The flank faces 27and 28 are provided with a recess in the region of the two lateralstrips 21 and 22, whereas above the lips 23 and 24, the distance betweenthe flank faces 27 and 28 is equal to the width of the cylindricalsurface 16.

Above the two lips 23 and 24, the flank faces 27 and 28 are annularsurfaces parallel to one another, adjoining which, further on theoutside in the radial direction, is a further recess having an axialdepth corresponding to the recess in the region of the strips 21 and 22.

The outer circumferential surface 29 is a surface of rotation concentricto the axis of rotation and is designed in a groove or channel shape, ascan be seen from FIG. 2. This results in a groove which runs in thecircumferential direction and has a curvature radius corresponding tothe distance of this outer circumferential surface 29 from the core of arope running over the pulley 1.

The reinforcing ring 14 is cohesively connected to the inner elastomericring 13 in the region of the circumferential surfaces 17 and 26, in theregion of the two strips 21 and 22, and in the region of the lips 23,24.

The raised lateral strips 21 and 22 are intended to prevent the cohesiveconnection between the surfaces 17 and 26 from tearing from the flank onaccount of the flexing movements which occur.

The ring 15, which is furthest on the outside in the radial direction,is likewise an elastomeric ring, which, however, has a greater hardnessthan the inner elastomeric ring 13. The material of the outerelastomeric ring 15 has a Shore hardness of between 70 and 95.

The outer elastomeric ring 15 is defined radially on the inside by aninner circumferential surface 31, radially on the outside by an outercircumferential surface 32 and laterally by two flank faces 33 and 34.The inner circumferential surface 31 has the same course and the sameform as the outer circumferential surface 29 of the reinforcing ring 14.

The two lateral flank faces 33 and 34 merge into two strips 35 and 36,which point radially inward and are formed in the radially outer recessin the flank faces 27 and 28 of the reinforcing ring 14. The two strips35 and 36 are laterally drawn in slightly, so that a slot 37 which runsin the circumferential direction is produced in the region of these twostrips 35 and 36 on each front face of the tire 3. The slots 37 are opentoward the flank of the tire 3.

The outer circumferential surface 32 is provided with a rope groove 38,the radius of curvature of which is approximately equal to the distancebetween the core of a rope running over it and the outer circumferentialsurface 32. The rope groove 38 is located centrally between the flankfaces 33 and 34.

A small V-shaped slot 39 or 41, respectively, is in each case providednext to both sides of the rope groove 38.

As in the case of the inner elastomeric ring 13, the outer elastomericring 15 is also cohesively connected to the reinforcing ring 14. Thecohesive connection between the surfaces 31 and 29 is in this case to beprotected from tearing by the lateral strips 35 and 36.

The cross-sectional form of the tire 3 and its individual rings 13, 14,15 forming it is constant along the circumference. The individualinterruptions in this course are blind openings 42, which extend fromthe flanks 27 and 28 into the reinforcing ring 14. These blind openings42 are intended to reduce the weight of the reinforcing ring 14 and thushelp to save material on the one hand and promote the heat dissipationfrom the interior of the tire 3 on the other hand.

In order to achieve this function, the two flange disks 12, which securethe tire 3 in place on the seating face 8 in the axial direction,contain corresponding openings 43, which as far as possible are inalignment with the blind openings 42 in the assembled state.

In addition, there may also be further through-openings (not shown) inthe flange disks 12, these further through-openings being located at alevel corresponding to the through-openings 45.

To assemble the tire shown in FIG. 2, first of all one of the two flangedisks 12 is screwed to the pulley body 2 by means of the fasteningscrews 11. The tire 3 is then pulled onto the seating face 8 in theaxial direction until it bears with the flank faces 27 or 28 against theinside of the fastened flange disk 12. The second flange disk 12 is thenmounted and fastened with the screws 11.

If a suspension rope of an aerial tramway for the conveyance ofpassengers or materials runs over the pulley 1 designed in this way, therope is directly in contact with the outer elastomeric ring 15. Sincethis ring 15 is made of a comparatively hard elastomer, good abrasiveresistance is achieved, whereas, on the other hand, the generation ofnoise is slight.

Due to the weight of the rope running over it, with the gondolas hangingthereon, the outer elastomeric ring 15 will be deformed to acomparatively small extent on account of its considerable hardness.

On the other hand, the inner elastomeric ring 13 is substantiallysofter, for which reason it will be deformed, although not only locally,but over its entire circumferential region. The reinforcing ring 14contained between the two elastomeric rings 13 and 15 distributes theforce originating from the weight of the rope in such a way that thereinforcing ring 14 becomes slightly eccentric relative to the seatingface 8. Directly below the rope supporting point, the inner elastomericring 13 is compressed, whereas it is stressed in tension at the locationdiametrically opposite this point relative to the axis of rotation. Onthe other hand, at two locations which are rotated exactly through 90°therefrom, only a shearing stress occurs in the elastomeric ring 13.Depending on which direction a shearing stress progresses starting fromthis location, the shearing stress decreases and turns into acompressive stress or changes to a tensile stress. In this way, theflexing stress of the tire 3 which occurs when the rope runs over it isuniformly distributed over the entire circumference of the inner ring13. Consequently, the inner ring 13 may be made of a comparatively verysoft elastomeric material, since the rope pressure is directed into therigid pulley body 2 over a relatively large area.

The soft elastomeric material may be provided with very little internaldamping, whereby the work occurring due to the flexing is kept small andthe inner elastomeric ring 13 heats up only slightly as a result of theflexing.

When the clamping socket, via which the stem of the gondola is connectedto the rope, runs over the pulley 1 described, a force directed downwardis briefly produced on account of the apparent rope thickening. Therelatively soft inner elastomeric ring 13 can readily yield to thethickening.

Since elastomers are known to be incompressible, a correspondingcross-sectional change is produced by the deformation as a result of therope force. So that this cross-sectional change can actually occur andis not blocked by the two flange disks 12, the two flanks 18 and 19 ofthe inner elastomeric ring 13 run toward one another. This results in awedge-shaped gap in each case relative to the two flange disks 12, thewedge-shaped gap being filled during the local compression of theelastomeric ring 13.

The lateral grooves 37 and the V-shaped slots 39 and 41 contained on thetop side have a similar function.

In order to vary the compliance, damping and abrasion behavior, theinner and/or outer elastomeric ring 13, 15, if need be, may containtextile inlays of metallic filaments, plastic or natural fibers. Inaddition, a textile inlay in the inner ring 13 can improve the frictiongrip between the tire 3 and the pulley body 2.

In the exemplary embodiment according to FIG. 2, the reinforcing ring 14is a plastic molding, if need be fiber-reinforced. If this strength isnot sufficient in order to adequately distribute the loading over thecircumference of the inner ring 13, a reinforcing ring 14, as shown inFIG. 3, may also be used. This reinforcing ring 14 consists of two ringhalves 14 a and 14 b, which have the same form and are arranged theopposite way round from one another. The reinforcing ring 14 obtained inthis way has essentially the same outer contour as the reinforcing ring14 according to FIG. 2, i.e. it forms a radial inner circumferentialsurface 26 which is continuous throughout and a radially outercircumferential surface 29 which follows the course of the rope groove38. The difference in the outer contour consists essentially in therecesses, which in a sheet-metal formed part can be designed with flankswhich are not so steep.

The ring half 14 a, in the same way as the ring half 14 b, is asheet-metal formed part of U-shaped cross section having an essentiallystraight leg 45, which is bent inward at its outer end at 46. Thesheet-metal formed part merges at 47 into a flat back 48, which in theassembled state runs parallel to a plane perpendicular to the axis ofrotation. This is followed in turn at 49 by a leg 51 which runs outwardand is designed in such a way that the desired outer form is obtained.

In order to obtain the complete ring 14, the two ring halves 14 a and 14b are arranged so as to bear against one another with their two backs 48and, for example along the two fillets resulting from this, are weldedto one another at 52 and 53.

Since the construction is otherwise the same as in the exemplaryembodiment according to FIG. 2, the remaining components do not need tobe explained further.

Shown in FIG. 4 is an exemplary embodiment in which the reinforcing ring14 again consists of two halves 14 a and 14 b produced as a sheet-metalformed part. These two halves 14 a and 14 b have a U-shaped form asviewed in cross section and are identical to one another. The essentialdifference from the embodiment according to FIG. 3 consists in the factthat the axial depth of the sheet-metal formed parts is slightlysmaller, so that, as can be seen in FIG. 4, the two backs 48 are at adistance from one another.

In order to fasten them to one another, the backs 48 contain holes 55which are uniformly spaced apart along the circumference and throughwhich cylindrical rivets 56 pass, which are riveted inside therespective profile while forming a closing head 57. As a result, itbecomes possible, during the production of the outer elastomeric ring15, to allow its material to pass radially inward through the gapbetween the two halves of the reinforcing ring 14. The reinforcing ring14 therefore no longer forms a boundary between the elastomeric outerring 15 and the elastomeric inner ring 13. On the contrary, in theexemplary embodiment according to FIG. 4, it is embedded in the outerelastomeric ring 15. The two elastomeric rings 13 and 15 meet oneanother directly at a boundary layer 58. This boundary layer has theform of a double cone with the orientation as follows from FIG. 4, i.e.the thickness of the inner elastomeric ring 15 is smallest at the centerbetween the two flange disks 12.

At the boundary layer 58, the two rings 13 and 15 may either becohesively connected to one another or are produced separately from oneanother in order to be fitted into one another subsequently.

Otherwise, the design of the tire 3 according to FIG. 4 corresponds tothe design of the tire 3 according to FIG. 2.

It goes without saying that the reinforcing ring 14 may also be embodiedas a metal casting or forging or may be assembled from such parts.

FIG. 5 shows another exemplary embodiment of the pulley 1 according tothe invention. The essential difference from the previous exemplaryembodiments consists in the use of an additional clamping device 61.

Whereas in the previous exemplary embodiments the pulley body 2 has theform of a spoked wheel, it is designed as a disk wheel in the exemplaryembodiment according to FIG. 5.

The seating face 8 for the tire 3 starts at one of the front faces ofthe seating face 8 with a short cylindrical section 62, which contains asnap-ring groove 63. Adjoining the cylindrical section 62 is afrustoconical surface 64, which is oriented in such a way that thediameter increases continuously from the cylindrical section 62 in thedirection of the opposite front face of the pulley body 2. The largestdiameter, relative to the axial extent of the pulley body 2, is reachedapproximately at the center of the latter at a plane of symmetry 65. Asecond frustoconical surface 66 starts at this location, but with theopposite orientation, i.e. the diameter tapers starting from the planeof symmetry 65. Finally, the frustoconical surface 66 merges into afurther cylindrical surface 67, which likewise contains a snap-ringgroove 168. The diameter of the two cylindrical surfaces 62 and 67 isidentical. The outer circumferential surface or the seating face 8,relative to the axis of rotation, is rotationally symmetrical, but nolonger cylindrical as in the previous exemplary embodiments.

As before, the radially outer ring 15 and the reinforcing ring 14 belongto the tire 3.

The radially outer ring 15 is relatively thin-walled and contains therope groove 38 in its outer side. The radially outer ring 15 is made ofa rigid plastic or an elastomer having a Shore hardness of between 80and 100.

In contrast to the previous exemplary embodiment, the reinforcing ring14, which is cohesively connected to the radially outer ring 15, forexample by vulcanizing, is comparatively thin-walled, relative to theradial direction. It is made of a similar material as explained inconnection with the previous exemplary embodiments. Its bore, unlike theprevious exemplary embodiment, is not a cylindrical bore, but has theform of a double conical frustum, consisting of two frustoconicalsurfaces 69 and 68, which are oriented in such a way that, relative tothe axial extent, a constriction is obtained in the center of thereinforcing ring 14. The angular areas of the conical surfaces 68 and 69are complementary to the conical surfaces 64 and 66 as formed on thepulley body 2.

The diameter of the two frustoconical surfaces 68 and 69, as FIG. 5shows, is markedly larger than the diameter of the two frustoconicalsurfaces 64 and 66. In this way, an annular gap, which is defined by atotal of four conical surfaces, is obtained between the reinforcing ring14 and the seating face 8.

The radially inner ring, which was unsplit in the previous exemplaryembodiments, is composed of two sections 13 a and 13 b in the exemplaryembodiment according to FIG. 5. The two sections 13 a and 13 b are inmirror symmetry relative to one another and are in each case thegenerated surface of conical frustums. Their axial extent isapproximately equal to the length of the conical generated surface 68 or69 respectively.

The clamping device 61 comprises two clamping rings 71 and 72, which areessentially in mirror symmetry relative to one another. The clampingring 71 is defined in the radial direction by two frustoconical surfaces73 and 74, which are oriented in such a way that they converge in thedirection of the plane of symmetry 65. Extending between the twofrustoconical surfaces 73 and 74 are two end faces 75 and 76. These endfaces 75 and 76 are flat faces in the broadest sense, the end face 75facing the plane of symmetry 65. The material of the clamping ring 71is, for example, steel.

The part 13 b of the radially inner ring is vulcanized in place on thefrustoconical surface 74. The cone angle of the frustoconical surface 74is selected in such a way that the frustoconical surface 74 runsparallel to the frustoconical surface 68. The same correspondinglyapplies to the frustoconical surface 73 relative to the frustoconicalsurface 66.

In order to achieve as good an elastic action as possible, a furtherelastomeric ring 77 is vulcanized in place on the radially innerfrustoconical surface 73, the elastomeric ring 77 being made of the samematerial as the radially inner ring 13 b. Its free surface 78 is in turna frustoconical surface, which runs parallel to the frustoconicalsurface 66.

Parallel to the axis of the pulley body 3, the clamping ring 71alternately has tapped holes 79 and stepped holes 81.

The clamping ring 72 has essentially the same form as the clamping ring71, for which reason the structural elements there are provided with thesame reference numerals as the structural elements of the clamping ring71. The clamping ring 72 also bears an additional elastomeric coating 77on its inside, which circumscribes a frustoconical bore 78. However,instead of the tapped holes 79, the clamping ring 72 contains steppedholes 82, which serve to receive fastening screws 83.

Finally, two identical flange disks 84, which are designed as flatdisks, complete the construction of the pulley 1, the bore 85 of theflange disks 84 having a diameter corresponding to the outside diameterof the two cylindrical sections 62 and 67. The bore 85 is defined towardthe outside by a bevel surface 86, in which a snap ring 87 finds spacein the assembled state when it is inserted into the snap-ring groove 63or 68.

The pulley 1 according to the invention is assembled as follows:

First of all the clamping ring 71 with the radially outer ring 13 bvulcanized in place and the elastomeric coating 77 is put onto thepulley body 3 from the left-hand side. The left-hand flange disk 84 isthen put on and the left-hand snap ring 87 is snapped into the snap-ringgroove 168. The unit consisting of the reinforcing ring 14 and theradially outer ring 15 can now be slipped on from the right without theclamping ring 71 being able to give way to the side. The right-handclamping ring 72 is then likewise put onto the pulley body 3 from theright. Once the arrangement has been prepared to this extent, theclamping rings 71 and 72 are rotated relative to one another until eachtapped hole 79 is opposite a stepped hole 82. Screws 83 are then screwedinto each combination of tapped hole 79 and stepped hole 82 andtightened one after the other. As a result of the frustoconical form ofthe two clamping rings 71 and 72 in combination with the frustoconicalsurfaces 64, 66, 68, 69, a radial clamping force is produced when thetwo clamping rings 71 and 72 are being screwed together, and this radialclamping force is directed, on the one hand, radially inward against thetwo frustoconical surfaces 64 and 66 and, on the other hand, radiallyoutward against the two frustoconical surfaces 68 and 69. The clampingrings 71 and 72 act like annular wedges, which are pressed between theconical surfaces 66, 68 and 62, 69 respectively.

Finally, the right-hand flange disk 84 is put on and secured by means ofthe right-hand snap ring 87 snapped into the snap-ring groove 63. Thepulley 1 is thus completely assembled.

The pretension, with which the two sections 13 a and 13 b of theradially inner ring, or the elastomeric coatings 77 on the inside of thetwo clamping rings 71 and 72 are pretensioned, can be regulated by moreor less pronounced tightening of the screws 83. The materials for thesections 13 a and 13 b of the radially inner ring are expediently thesame as for the elastomeric coatings 77 and they also have the same wallthickness. In this way, the elastomeric coatings 77 also have an elasticaction when a clamping socket runs over the pulley and attempts to pushaway the outer circumferential surface of the tire radially relative tothe hub 5.

The pretension, caused by the clamping rings 71 and 72, in the radiallyinner ring 13 a or 13 b and in the elastomeric coating 77 acts in such away that the radially inner ring 13 a or 13 b and the elastomericcoating 77 are not deformed further until after a certain radial force,determined by the pretension, is exceeded. However, the furtherdeformation takes place with the same hardness or softness, as if therewere no additional pretension. In this way, the flexing work can bereduced when, for example, only the empty rope runs over the pulley 1.Deformation of the radially inner ring 13 a or 13 b or of theelastomeric coatings 77 and consequently also flexing work result onlywhen greater forces occur.

As a result of the radial pretension, the reinforcing ring 14, togetherwith the radially outer ring firmly vulcanized on it, is reliably heldin place on the seat 8 in a frictional manner. If the friction grip isnot sufficient, it is also possible to cohesively connect the coating 77to the frustoconical surface 64 or 66 during assembly, for example if anadhesive is introduced during assembly or if the boundary surface issubsequently vulcanized after assembly. The same can be done between thefrustoconical surface 68 or 69 and the outside of the radially innerring 13 a or 13 b.

Conversely, as follows from the explanation of the assembly, dismantlingis readily possible in a simple manner by the above mentionedmanipulations being carried out in the reverse sequence. In this way,the tire 3, which is subject to wear, and/or the clamping rings 71, 72can be exchanged even when a pulley is mounted on a mast.

A pulley consists of a pulley basic body which has a cylindrical outercircumferential surface. Sitting on this cylindrical outercircumferential surface is a tire, which is of sandwich-like design withregard to its radial extent. This results in a plurality of ringsconcentric to one another. The ring which is furthest on the inside inthe radial direction and the ring which is furthest on the outside inthe radial direction is in each case an elastomeric ring, whereas areinforcing ring is located between them. The elastomeric outer ring isharder than the elastomeric inner ring, so that a veryabrasion-resistant surface is achieved, over which the rope runs,whereas the elastomeric inner ring provides for adequate resilience. Thereinforcing ring is provided in order to distribute the rope load asuniformly as possible over the elastomeric inner ring.

1. A pulley comprising: a pulley body which has a rotationallysymmetrical outer circumferential surface and a pulley hub, and having atire which sits on the outer circumferential surface and has at leastone radially outer and one radially inner ring and also a reinforcingring, the reinforcing ring being made of a material which is rigidrelative to the radially inner and the radially outer rings, thereinforcing ring having a diameter which is smaller than the outsidediameter of the radially outer ring, the radially inner ring being madeof an elastomer, the radially outer ring being made of an elastomer or aplastic, and the radially outer ring having a greater Shore hardnessthan the radially inner ring, wherein the reinforcing ring consists oftwo parts which are joined together along a radial plane and arefastened to one another.
 2. The pulley as claimed in claim 1, whereinthe two parts of the reinforcing ring bear directly against one another.3. The pulley as claimed in claim 1, wherein the two parts of thereinforcing ring are connected to one another while forming at least oneaxial intermediate space.
 4. A pulley comprising: a pulley body whichhas a rotationally symmetrical outer circumferential surface and apulley hub, and having a tire which sits on the outer circumferentialsurface and has at least one radially outer and one radially inner ringand also a reinforcing ring, the reinforcing ring being made of amaterial which is rigid relative to the radially inner and the radiallyouter rings, the reinforcing ring having a diameter which is smallerthan the outside diameter of the radially outer ring, the radially innerring being made of an elastomer, the radially outer ring being made ofan elastomer or a plastic, and the radially outer ring having a greaterShore hardness than the radially inner ring, wherein the outercircumferential surface of the pulley body forms a double cone, whichhas the largest diameter at the intersection between the two cones.
 5. Apulley comprising: a pulley body which has an outer circumferentialsurface; and a tire which is disposed on the outer circumferentialsurface and which comprises: an outer ring; a separate inner ring; and areinforcing ring interposed between the outer ring and the inner ring,the reinforcing ring being made of a material which is rigid relative tothe radially inner and the radially outer rings and which has at leastone portion which is at least as thick as the radially outer ring, theradially inner ring being made of a first material, the radially outerring being made of a second material having a greater Shore hardnessthan the material of the radially inner ring.
 6. A pulley as claimed inclaim 5, wherein the reinforcing ring has a non-uniform cross-sectionand is thicker at the sides than in the middle.
 7. A pulley as claimedin claim 5, wherein the reinforcing ring has an indented cross-sectionalprofile.
 8. A pulley suitable for use in an aerial tramway, comprising:a pulley body which has a rotationally symmetrical outer circumferentialsurface, a pulley hub, a radially outer ring made of an elastomericmaterial and forming a groove for receiving a cable, a stiffening ringprovided radially within the diameter of the groove, a radially innerring made of an elastomeric material that is softer than the elastomericmaterial of the outer ring, and a clamping device provided to secure theradially outer ring, the stiffening ring and the radially inner ring onthe pulley hub.
 9. The pulley as claimed in claim 8, wherein a theclamping device includes a mechanism for radially pretensioning theradially outer ring on the outer circumferential surface of the pulleybody.
 10. The pulley as claimed in claim 9, wherein the clamping device,relative to the axial direction of the pulley body, is split into twoannular parts.
 11. The pulley as claimed in claim 10, wherein theradially inner ring, relative to the axial direction of the pulley body,is split into two parts, and in that in each case one part of theradially inner ring sits on the corresponding part of the clampingdevice.
 12. The pulley as claimed in claim 10, wherein each annular partof the clamping device has a frustoconical outer form and afrustoconical bore, the radial thickness at one axial end of eachannular part being smaller than at the other axial end, and in that aring is obtained in an assembled state, which ring, relative to itsaxial extent, is constricted approximately in the center.
 13. The pulleyas claimed in claim 10, wherein the two annular parts are screwedtogether by means of screws.
 14. The pulley as claimed in claim 8,wherein the clamping device has an annular, essentially rotationallysymmetrical form with a radially inner and a radially outer surface. 15.The pulley as claimed in claim 8, wherein the clamping device, relativeto the radial direction, is fitted in between the radially inner ringand the outer circumferential surface of the pulley body.
 16. The pulleyas claimed in claim 8, wherein the clamping device, relative to theradial direction, is fitted in between the radially inner ring and thestiffening ring.
 17. The pulley as claimed in claim 9, wherein theclamping device bears an elastomeric coating on its radially innersurface, said elastomeric coating being cohesively connected to theclamping device.
 18. The pulley as claimed in claim 17, wherein theelastomeric coating is made of the same material as the radially innerring.
 19. The pulley as claimed in claim 8, wherein the radially outerring is arranged on the outer circumference of the stiffening ring. 20.The pulley as claimed in claim 8, wherein the radially inner ring isnon-detachably connected to the clamping device.
 21. The pulley asclaimed in claim 8, wherein the clamping device is axially divided intotwo parts that clamp in the axial direction.
 22. The pulley as claimedin claim 21, wherein the radially inner ring is axially divided into twoparts and each part is secured to one of the two parts of the clampingdevice.
 23. The pulley as claimed in claim 21, further comprisingfasteners connecting the two parts of the clamping device to oneanother.
 24. The pulley as claimed in claim 23, wherein the fastenersare threaded fasteners.
 25. The pulley as claimed in claim 8, whereinthe radially inner ring is axially divided into two parts.
 26. Thepulley as claimed in claim 8, wherein the reinforcing ring is embeddedin one of the radially outer and the radially inner ring.
 27. The pulleyas claimed in claim 8, wherein the stiffening ring is a sheet-metalformed part.
 28. The pulley as claimed in claim 8, wherein thestiffening ring is a forging.
 29. The pulley as claimed in claim 8,wherein the stiffening ring is a casting.
 30. The pulley as claimed inclaim 8, wherein at least one of the radially outer or the radiallyinner ring is connected to the stiffening ring in a positive-lockingmanner.
 31. The pulley as claimed in claim 8, wherein the stiffeningring is fiber-reinforced.